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Water

Boiling: Handy to know the answer if you are out backpacking or taking a trip to the less civilized parts of the world. Common options are to use chlorine, a ceramic filter, iodine tablets or to boil the water to treat it. Boiling water is the only known method that is 100% effective in destroying pathogens known to cause sickness. The Centers for Disease Control have a very handy chart comparing the effectiveness of various water treatments.

True. Bees don’t usually fly more than 3 miles from their nests and must have a constant water source. So watching the direction they fly when leaving the nest can be a valuable tool for locating water. Flies stay even closer to water – about 100m or so.

Cold water forces a rapid, uncontrollable gasping in everyone and that lasts from 1-3 minutes. If you happen to gasp while your mouth is underwater, you will draw the cold water into your windpipe and lungs which can then spasm and contract. Even if you manage to get your mouth above water, you may still not be able to clear the water and get enough oxygen. If things go really wrong, your epiglottis may spasm closed and you will dry drown. (The epiglottis is the cartilage flap that keeps liquid out of your lungs when you drink.)

There is some evidence that keeping the cold water off your face and head may lessen the gasp reflex. That is why you want the life jacket on before you hit the water. It helps to keep your face and mouth out of the water. The initial immersion in cold water causes a sudden constriction of surface blood vessels which causes an immediate jump in blood pressure and heart rate; sometimes to maximum heart rate. If your heart cannot handle this jump, it stops and you die. This seldom happens in healthy and fit people but the danger is still there. If you have a choice, make sure to wear a life jacket that is self-righting so that it keeps your face out of the water if you are unconscious....

Water is absolutely essential to life1. In survival situations, there is something known as The Rule of Threes. It says that you can survive 3 minutes without air, 3 hours in inclement weather, 3 days without water, 3 weeks without food. We are going to assume that you don't have to worry about air to breathe or freezing to death as you begin your journey from hatchet in the woods to sending an email. That makes finding fresh water your highest priority.

It's no wonder that the first great civilizations emerged alongside freshwater rivers such as the Nile, the Tigris, the Euphrates, the Indus and the Yangtze. These fresh water sources provided the large quantity of water needed for farming. You can clearly see the Nile from space at night. (Click on the image at right for a larger view)

Fresh water is scarce

Even though the Earth’s surface is 70% water, 97% of it is salt water. Of the 3% that is fresh water, all but about 1% is locked up in ice at the poles. That means only 1% of the water on Earth is really useful to humans. That makes fresh water a relatively scarce resource1. To put that in another perspective: Imagine if you could only use 1% of the money in your wallet. What could you buy with that?

It literally comes from the sky

The hydrologic cycle describes how fresh water is created by the sun. The heat from the sun causes the water of the surface of the Earth to evaporate. When the water evaporates it leaves behind the salt and other minerals that it had in it. When it condenses again and falls to the Earth (in the form of precipitation), it is fresh water. It will either drain back to the ocean or be evaporated again. This cycle just keeps repeating.

1The English word ‘rivals’ comes from the Latin word rīvalis , which literally means : one who shares the same brook. The notion being that neighbors compete for a precious resource.